The present invention relates generally to the art of welding-type power supplies. More specifically, it relates to welding-type power supplies used with robots or other peripherals.
Welding power supplies or systems are available for a wide variety of processes, and with a wide variety of sophistication. Welding-type power supply or system, as used herein, includes power supplies or systems that provide welding, cutting or heating power, and may include a controller, switches, etc. Traditionally, a good weld required an experienced welder, not only to properly execute the weld, but to properly select operating parameters (such as output voltage, current, power, arc length (trim), pulse width, wire feed speed, etc.)
Now, robots are available that execute the weld. Also, operating parameters may be pre-determined and automatically implemented by a controller in the robot. The program attempts to implement and improve upon the decisions that had been made by the experienced welder. The robot must be able to accurately command the other devices in the weld cell to effectively carry out the programs.
Unfortunately, various errors can be introduced in the system, particularly from the connection between the robot and the welding power source. For example, digital robot command data is converted to an analog value and sent to the welding-type power supply. The power supply converts this analog command to a digital signal and processes it for the desired weld. Data converters on both ends of the system (robot and power supply) can introduce errors to the command signal. Signal distortion can also be introduced by the resistance in cables and connectors. Every welding-type system can have a unique combination of signal errors depending on factors such as wear, equipment age, and other possible environmental factors.
This can cause a problem, particularly when systems are used for the same application. Because the errors may vary between the two systems, two welding-type systems running identical programs on identical work pieces could produce two different welds.
The prior art required the user to adjust the command from the robot to achieve the desired result. For example, if the user wanted 100 ipm wire feed speed, the user can initially set the robot at 100 ipm (or close to it), and monitor the actual output. Then, the user adjusts the requested speed until the desired speed is obtained. If, at 100 ipm, the error is xe2x88x924%, the user would end up requesting a wirefeed speed of 104 ipm at the robot to obtain, after the error, 100 ipm at the welder. Alternatively, the user could go down to the board level and tweak potentiometers in the welder to try to achieve the desired result. Of course, neither solution is desirable, and requires extra work from the user. Also, to the extent the error is not constant, the user has to calibrate for each different setting.
Accordingly, a simple calibration that doesn""t require removal of any panels, permits the synchronization between the robot and welding power supply, and improves installation and long term maintenance of the welding system is desired.
According to a first aspect of the invention a method of calibrating a welding-type power supply and a robot includes entering a calibration mode (in the welding-type power supply) and providing two predetermined commands (for a welding parameter) from the robot to the welding-type power supply, and comparing them to two standards. A command scaling curve for the parameter is calculated in response to the comparisons.
According to a second aspect of the invention a method of calibrating a welding-type power supply and a robot includes providing a weld schedule to the robot. The schedule has at least two (different) settings for one welding parameter. A calibration mode is entered in the welding-type power supply, and the robot provides two commands corresponding to the two settings. The received commands are compared to expected commands for the settings. A command scaling curve for the parameter is calculated in response to the comparisons.
According to a third aspect of the invention a welding-type power supply that may be connected to a robot includes two comparison modules that receive two predetermined commands from the robot, and also receive two standards. The commands and standards correspond to a welding parameter. A curve fitting module receives the results of the comparison modules, and provides a command scaling curve output.
According to a fourth aspect of the invention a welding-type power supply that may be connected to a robot includes a calibration module that has a weld schedule input and a command output. It also has a comparison module that receives the command output and two standards. The command and the standards correspond to a welding parameter. A curve fitting module receives the output of the comparison module, and provides a command scaling curve output.
Two predetermined commands, relating to a different welding parameter, are provided from the robot to the welding-type power supply, and compared to two more standards in one embodiment. A second command scaling curve for the second parameter is calculated in response to the comparisons.
According to various alternatives the parameter(s) includes wire feed speed, voltage and arc length (trim).
Feedback from the welding-type power supply is provided to the robot that is indicative of a commanded output in another embodiment.
The settings are predetermined in one embodiment, and user-determined in another embodiment.
The weld schedule has a third setting for the parameter and the robot provides a third command (corresponding to the third setting) to the welding-type power supply. The third command is compared to a third expected command for the third setting, and the calculation is done in response to the comparisons to the first, second and third expected commands.
The first and second standard inputs are provided by a user interface or a memory in other alternatives.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.